The present invention relates to the general field of sonic energy, and more particularly relates to a sonic motor and system adaptable for a variety of uses.
Sonic energy is utilized in a number of fields, and the term "sonic" as defined herein is intended to include the frequency range from 1 KHz to 1,000 KHz. In all of these applications a sonic motor is utilized that converts electrical energy to sonic mechanical vibrations. The prior art illustrates a number of patents defining various types of motors adapted for particular uses. Certain of the sonic applications require a motor that produces radially directed mechanical vibrations which are coupled or transmitted to a surrounding medium. In the area of underwater technology this medium is generally water that transmits these radially directed beams of energy for various uses well known in the art.
Prior to the present invention these radially directed vibrations utilized in a device to act as a sonic beacon buoy, etc., in a sea water environment, as well as other applications, utilized a transducer that was vibrated in a radial mode. To obtain the vibration of the transducer, generally made from a piezoelectric element, either a cylindrical tubular element was used or a flat disc having a circular peripheral surface. A piezoelectric element formed as a cylinder or a disc can be vibrated in a radial mode in accordance with well known characteristics.
It has been found in accordance with the present invention that the drawbacks of utilizing a cylindrical or disc shaped piezoelectric crystal or element can be avoided by the utilization of a longitudinally vibrating transducer and a means for transforming the mechanical vibrations through a transmission member into radial vibrations at a loop of longitudinal vibration. By being able to accomplish this transmission in an efficient manner, the problems associated with a cylindrical or disc shaped element is avoided. For example, when vibrating a piezoelectric element in a radial mode, the coupling coefficient is generally relatively low since a loss of energy occurs through the bonding agent that has to be employed. This low efficiency factor requires a larger power source in order to obtain the same output amplitude of the motor.
Applicant has now discovered that longitudinal vibrations may be utilized to vibrate a cylindrical transmission member coupled to the transducer at a loop of longitudinal vibration which is then transformed into radial vibrations in the transmission member and in turn coupled to the housing means of the motor with a high energy efficiency.
The sonic motor of the present invention has found ideal usage in devices as locaters or position indicators in connection with underwater objects, or as safety or rescue devices in connection with sea water. The principles of the invention may be used in any useful way, whether or not in a device for use on or in the sea.
In accordance with one aspect of this invention, the sonic motor may be incorporated in a device or system which is automatically activated when positioned in sea water. For example, a device made in accordance with the invention may be stored for long periods of time and be freshly activated by the addition of a salt water solution at the time use is desired.
The self-powered sonic marker, beacon, or buoy comprises a sea water powered sonic transmitter for undersea applications where a site, a structure, equipment such as pipe lines, cables, fishing trawls, wrecks, etc., or any other object might normally be difficult to locate. The sonic marker buoy transmits sonic energy either as a continuous sinusoidal wave or as intermittent bursts of waves occurring at a predetermined number of bursts or pulses per second. By placing this marker as a buoy on or in the vicinity of such a site, etc., the use of a receiver capable of detecting this sonic energy will aid in localizing the object so marked.
The invention, as it relates to underwater uses, is unique in that it does not employ a battery (in the everyday concept of a dry cell, etc.) to power its electronic circuitry but utilizes the electrical voltage produced when two dissimilar metals such as copper and magnesium are immersed in a salt solution such as sea water. It therefore does not depend on the limited life of a storage cell or other forms of batteries normally used for powering electrical circuits. The marker buoy has a useful life governed only by the corrosion by sea water of the magnesium electrode. In practical applications and configurations, it appears that a useful life of several years can be expected from a marker buoy such as described herein.
The ability to increase the efficiency of the system by transforming the longitudinal motion to radially directed vibrations that is easily coupled to the housing means containing the transducer means forming part of the motor greatly increases the acoustical efficiency of the device.